Sometimes we have to get our priorities straight. While i've gone the extra mile for exes too, my
kids came first and because i was a single Mom for much of their childhoods, i learned the hard but necessary lesson that if we don't take good care of ourselves we can't take care of others either. Considering how much your daughter has stepped up for you it is hard not to think the kids have good reason to have disassociated from their Dad and to want you to do so also. If a job or substance (your use of it) was causing this must havoc in your life and distress for your children--you'd realize you needed to make changes, right? Sometimes we get addicted to both to other people and to our own self-image. We want to be kind and take care of anyone we've ever loved--but we have to face the fact that we are not responsible for the situations others get themselves into--they are!!! And if they won't accept reasonable life-improving suggestions, you have to let them muddle thru their own mess.
Don't know where you live but most states have senior center networks. NM is considered one of the poorest states, yet even my small town (approx 800 residents) has a senior center that serves it and smaller nearby communities, also has a dialysis center. Of course that's probably why we're ranked as poor because taxes actually get spent on things that help people. You have to talk to his doctor, who may not even realize he's still driving, and to DMV in your county.
STRESS is the biggest mitigator of all disease processes, it makes healing, even with best of treatment more difficult. You have to take care of you, or he's going to be all alone and in deep trouble anyway. If talking to him about it in that context doesn't move him to make the needed adjustments, for your sake and your children's i hope you can find the emotional courage to walk away from him. He is clearly as destructive to your life as any substance addiction can be.
As i was writing all that, a question occurred to me: What would he do if his car simply could not run anymore? Does he have a way to get another? (Money and means?) Such a turn of events might make him realize that moving into assisted living or checking with state agencies (sometimes they can arrange part time care givers/drivers on a sliding scale fee basis that might be less than upkeep on a vehicle) might be a smarter thing to do. (Some of the guys might be able to guess what i'd have done by now if he'd have to make changes if something happens to current car in a way that he couldn't replace it due to insurance $$. )
i'm not going to tell you what i'd do despite my natural helping instincts. You're not me, what works for me (setting my priorities, letting the other person know i have to withdraw from doing things for/with them, and setting a deadline for that withdrawal unless they take verifiable actions toward resolving their difficulties and sticking to it) probably wouldn't work you as evidenced by your responses to the good suggestions you've received.
My daughter actually had a talk with me (and she was 16 at the time) similar to some of the things i said in previous paragraphs to you, when several weeks after we moved my last husband to his own apartment (yes, DD and i actually transported his furniture and belongings for him) i was still getting up at 5 a.m. to drive him to his 6 a.m. shift at his job tho it was an easy walk from his new place.) i had health issues myself at the time and was working full time too. So i get it, i do. i hope you will find a way to prioritize your own well-being.